Using Pocket Diagnostic® plant disease rapid tests is straightforward. However, as with any rapid test procedure, attention to detail will pay dividends. Here are some ‘golden rules’ to maximise the performance of the tests:
Rule 1: Sample selection
Sample selection is key to achieving a reliable result. Points to note include:
- Don’t use too much tissue (0.2g or a 25mm square piece of leaf is sufficient)
- Take symptomatic tissue, include if possible the junction between healthy and diseased material
- Don’t use dead tissues
- If sampling a large plant, combine material from several places
- Wash soil off root samples
- Check Keycards for specific information on sampling.
Remember: avoid the temptation to add more sample just ‘for good measure’. Too much sample tissue will cause the test device to run incorrectly.
Rule 2: Sample preparation
Thorough extraction of the pathogen (e.g. virus particles, fungal mycelia) from the tissue sample is essential. In general, the tougher or woody the sample, the more shaking is required.
For example, bark samples should be cut up finely and shaken in the buffer for 60 seconds. Leaves with a thick cuticle should be cut or scored before adding to the extraction bottle.
Remember: you can’t ‘over shake’ the bottle, but insufficient shaking will reduce test performance.
Rule 3: Sample loading
Start the test by adding two drops of liquid from the extraction bottle. Avoid drawing sample debris or air bubbles into the pipette as these will interfere with the test.
If you don’t see the liquid front moving across the viewing window on the test device, add one more drop – but avoid flooding the device. The correct size of the drop is achieved when the pipette is held vertically.
Keep the test device horizontal when loading and running the test.
Remember: don’t add too much sample to the test device. If an air bubble does stop the test running, try squeezing the housing gently to release it.
Some other points to keep in mind
1. Keep warm
Tests run very slowly below 10oC. If using in cold conditions, warm the test device and buffer bottle in your hand first, or even better, keep them in your pocket before use.
2. Open and use
Once the foil pouch is opened, use the test. Moisture affects the performance of the kits, so don’t open until you need to use.
3. Ignore late-comers
All Pocket Diagnostic® plant disease rapid tests run fully in 10 minutes or under. Read the test result no later than 10 minutes, and ignore any changes which occur after this time.